One of the more serious aspects of the pathogenesis of Toxocara canis infection in man is the production of lesions in the eye. Aside from histologic data on enucleated human eyes, little is known about the onset, persistence and nature of these lesions. A study will be made in experimental animals to determine the distribution and survival of larvae in the eye at various intervals after infection, to study the development of associated lesions and to assess the role of immune reactions in pathology.